As is generally well known to persons familiar with the art, the air brake systems in railway cars include a large number of component parts for applying either service brake pressure or emergency brake pressure to the car's brake pipe. Two of such common components are a railway car control valve pipe bracket and an access plate. Each of these two component parts are provided with a plurality of small airway ports through which a portion of the compressed air of the air brake system must pass, and such air way ports are normally provided with a press-fitted filter insert for filtering-out any particulate matter entrapped within the air passing therethrough. The press-fitted filter inserts are provided with a circumferential wall portion sized to engage a circumferential wall portion of the airway ports so as to be tightly maintained within the port not permitting any air leaks therearound. While the airway ports in such control valve pipe brackets and such access plates are very nearly the same size, they are not in fact quite the same, and hence the filter inserts as are to be fitted within the airway ports of the two components are not identical and hence not interchangeable. Specifically, the diameters of the airway ports into the DPX Pipe Brackets are approximately 10% smaller than those of the SCTD Access Plates. However, because of their similarity in size and appearance, it would not be unexpected for service personnel to mistakenly insert the wrong filter insert into either a control valve pipe bracket or an access plate with the result that the hardware will not function properly.
Besides the above operational problems that can result, the need to manufacture, maintain, stock, catalog, ship, etc. two different filter insert types adds considerably to the costs of manufacturers, suppliers and service facilities.